1. Field of the Invention
The invention relates to a locking nail system for arthrodesis reconstruction of calcaneus fractures. The invention can, in particular, be used in the reconstruction of severe comminuted fractures of the calcaneus in humans and fixation of this bone after reconstructing its principal form, to the talus, in order to attain arthrodesis or fusion with the latter.
2. Discussion of Background Information
Chronic residual pain is the most common sequela following comminuted talar fracture of the calcaneus. There may be multiple causes of this problem such as compartment syndrome, reflex-sympathetic dystrophy, plantar cushion syndrome, tarsal and peroneal canal syndrome, and subtalar arthritis. This latter cause has been found to be responsible for the majority of poor long-term results of current treatment of these fractures.
Talar fractures account for 8-10% of tarsal tunnel syndrome, particularly in the lateral plantar nerve branch, and for 78% of peroneal nerve entrapment (external submalleolar pain). In 70% of these severe fractures, there is chronic pain caused by the posterior subtalar joint, which normally becomes ankylosed after trauma.
Although the latest publications support the results of open reduction and internal fixation of calcaneus fractures, orthopaedic treatment still has many defenders. In other cases, the adoption of an initially conservative philosophy is chosen, treating sequelae if they appear. Like Barnard and Odegard, Applicant believes that perfect restoration of the subtalar joint is impossible.
Numerous arthrodesis techniques have been disclosed for the treatment of post-traumatic subtalar arthritis, including prosthetic replacement. In other cases, triple arthrodesis has been advocated over isolated subtalar fusion, in order to improve foot biomechanics and to prevent degeneration of adjacent joints. According to different reviews (conducted in hospitals), isolated arthrodesis of the subtalar joint does not cause degeneration of adjacent joints, even after many years of evolution.
This experience has led to the belief that the old postulations of Stulz and Noble may provide the key to a fracture that has yet to be resolved. Since the subtalar joint cannot be surgically reconstructed in the most severe fractures (and always degenerates), the solution would be to arthrodese it immediately during the acute period in order to prevent the disabling sequelaes that appear during later evolution.
However, in addition to fusing the damaged joint, an attempt should be made to reconstruct the form of the hindfoot as far as possible, in order to avoid other associated complications such as compartment syndrome, reflex-sympathetic dystrophy, plantar cushion syndrome and tarsal and peroneal canal syndromes, that would clearly benefit from fracture reduction.
Spanish publication number ES 2164543 discusses a nail that is locked by means of two screws. There are problems, however, inserting this nail into the bone because of its rectangular wedge-shaped geometry. There are also resistance problems since it has a very small section in the distal zone that also limits the securing of the lower screw.